Remains of giant armoured fish dug up…in the Sahara

An artist’s impression of Titanichthys, the giant armoured fish that swam the seas 380 million years ago (Credits: Mark Witton / SWNS)

A giant armoured fish that roamed the prehistoric seas 380 million years ago has been dug up… in the Sahara.

And it could hold the key to saving the world’s two biggest fish – the basking shark and the whale shark.

Named Titanichtys, it too was a filter feeder – swimming slowly with jaws ajar and straining zooplankton instead of sucking water in.

Basking sharks, so named because they often look like they are basking in the sun, and whale sharks do the same – today.

Only closing their mouths to swallow, long comb like structures known as gill rakers trap and filter food particles. They can strain up to 2,000 tonnes of water an hour.

The endangered creatures reach lengths of up to 40 and 60 feet, respectively. Baleen whales are among a number of marine animals that also use the technique.

Now an enormous three foot head belonging to Titanichtys may improve conservation efforts, say British scientists.

The remarkably preserved specimen dates back to the Late Devonian – 140 million years before the first dinosaurs roamed the earth.

At the time the world’s biggest sand desert was covered by a deep ocean teeming with life.

Fossils used in the study, as they were found in Morocco. (Credits: C. Klug / SWNS)

Swimming slowly with its mouth wide open, Titanichtys fed all day on tiny plankton to keep its huge body well nourished.

It was among the largest animals of the time – reaching up to twenty feet long and weighing more than three tons.

Its bones were so big it was once thought to be a dinosaur. But Titanichthys belonged to an extinct group of bizarre marine creatures called the placoderms.

Their heads and thoraxes were covered by articulated plates – and the rest of the body was scaled.

Lead author Sam Coatham, who carried out the research while studying for his masters in palaeobiology at the University of Bristol, said: ‘We have found Titanichthys was very likely to have been a suspension-feeder (filter feeder).

‘Its lower jaw was considerably less mechanically robust than those of other placoderm species that fed on large or hard-shelled prey.

‘Consequently, those feeding strategies – common amongst its relatives – would probably have not been available for Titanichthys.’

Placoderms were among the first fish to evolve jaws. Most were predators – setting Titanichthys apart.

It shared features with modern plankton-slurping fish including a lack of teeth, a large body size, relatively small eye sockets and long, slender lower jaws.

Fossils found in North America, Morocco and Poland show it shared the seas with many other strange fish.

These included the 30 foot long fanged sea monster Dunkleosteus – one of the scariest animals that ever lived. It had a thick body, bulging head and massive jaws.

Mr Coatham said: ‘The lower jaw of Titanichthys we investigated was over three feet long and still slightly incomplete – so it was definitely large.’

It was found in Morocco by co-author Professor Christian Klug, a palaeontologist at the University of Zurich, in a remote mountain range known as the Anti-Atlas.

Mr Coatham, who is now at the University of Manchester, added: ‘Titanichthys fossils have been observed with puncture marks caused by Dunkleosteus – an apex predator and one of few species which approached the size of Titanichthys.

‘I suspect Dunkleosteus would have been one of its only potential predators – akin to modern basking sharks only being predated by killer whales and potentially great white sharks.’

Unlike its similarly giant contemporary there is no previous evidence of how Titanichthys fed.

Where the lower jaw of Dunkleosteus and many of its relatives had clear fangs and crushing plates, Titanichthys’ is narrow and lacking any teeth or sharp edges suitable for cutting.

Consequently, Titanichthys was a ‘filter-feeder’, capturing high concentrations of plankton.

But no evidence of the comb-like projections that cover the gills of modern fish that do this have ever been found in the fossil record.

So the international team demonstrated it in Titanichthys indirectly – using bio-mechanical analysis to compare its lower jaw with those of other species.

The findings reported in the Royal Society journal Open Science are based on the fossilised skull unearthed by Prof Klug.

The Sahara desert used to be an ocean teaming with fish (Credits: Diego Mattarelli / SWNS)

He explained: ‘When you do field work in the Anti-Atlas, massive skull bones of placoderms can be found quite frequently.’

The team tested the resilience of the jaws by virtually applying forces using a technique called FEA (Finite Element Analysis).

This revealed the lower jaw of Titanichthys was much less resistant to stress and was more likely to break than those of the other placoderm species – such as the famous Dunkleosteus.

So the jaw of Titanichthys would not have been able to withstand the higher stresses associated with their strategies of feeding on large prey – which exerts more mechanical stress.

This pattern was consistent in both sharks and whales, with filter-feeders proving less resistant to stress than other species within the same lineage.

Further analyses comparing the distribution of stress across the jaws showed similar patterns in Titanichthys and the basking shark – reinforcing the results.

It has been established that there were almost certainly giant filter feeding vertebrates living 380 million years ago.

Mr Coatham said: ‘Our methods could be extended to identify other such species in the fossil record and investigate whether there were common factors driving the evolution and extinction of these species.

‘We suggest a link between oceanic productivity and the evolution of Titanichthys, but this should be investigated in detail in the future.

‘An established link could have implications for our understanding of the conservation of modern suspension-feeders.’

Large shark populations are plummeting due to overfishing and the shark fin trade. The fish are slow growing, late maturing and produce few young compared to other fishes.

These characteristics make them especially vulnerable to exploitation by humans.

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